Summary The article deals with the phonetic and orthographic adaptation of Latin terms in English clinical terminology in the context of Latin terminological competence formation of foreign medical students with English as the language of instruction. About 8,000 of the most common clinical terms selected from various lexicographic English sources have been studied on the basis of etymological and comparative approaches to demonstrate the grade of inconsistency in the reflection of Latin terms in modern English medical terminology. The quantitative analysis allowed us to determine and classify the main tendencies in the process of phonetic and orthographic development of Latin terms: (1) imitation of classical Latin spelling; (2) ‘simplification’ of classical Latin spelling; (3) syncretism of the first and second tendencies (parallel use of classical Latin and ‘simplified’ variants as synonyms). The analysis has also identified in some cases the phenomenon of ‘hypercorrectness’. The lack of a unified norm is reflected in all the analyzed reference sources, complicating the lexicographic description of medical terms as well as the process of teaching / learning the medical terminology. The proposed solution is to develop and implement some unified criteria for phonetic and orthographic adaptation of Latin terms in English. The possible ways to solve the problem are either to adhere to the etymological principle, returning ad fontes of medical terminology, and to use only non-monophthongized and non-simplified forms or to use monophthongized and phonetically and graphically simplified forms following the norms of modern English. Consistent adherence to one system of rules for the development of Latin terms is a needed requirement for the proper formation of terminological competence in medical students and correct use of terminology in their further professional activity.